Limiting Reactants • A chemical reaction will stop when you run out of one of your ______ • ______– limits the extent of the reaction. § Determines the amount of product that is formed. § It runs out first • ______– left over reactant
Limiting Reactant Problems • A limiting reactant problem can be easily identified because you have TWO givens • You basically are just going to do 2 stoichiometry problems
Steps 1. Write the ___________ 2. Start with given #1 and go to desired 3. 4. product Start with given #2 and go to the same product The one that formed the ______ amount of grams is the limiting reactant
Example • S 8 + 4 Cl 2 4 S 2 Cl 2 • 200. 00 g of S 8 and 100. 00 g of Cl 2 are combined in a flask. How much S 2 Cl 2 will you get?
Other questions • What was the limiting reactant? • What was the excess reactant? • How much excess did we have left over after the reaction was completed?
Another Example • P 4 + 5 O 2 P 4 O 10 • If we used 25. 4 g P 4 and 50. 0 g O 2 answer the following questions. 1. 2. 3. 4. 5. What is the limiting reactant? What is the excess reactant? How much P 4 O 10 will you get? How much excess did you use? How much excess will you have left over?
Another Example 1. What is the limiting reactant? 2. What is the excess reactant? 3. How much P 4 O 10 will you get? 4. How much excess did you use? 5. How much excess will you have left over?